Most of the merchants I've sunk so far (1939, September) ran at a steady 11 kts and I nailed them right amidships all the time with manual targeting. Except for the one time I made the mistake of using an electric with magnetic pistol, which ran straight under the keel without as much as a peep. But still amidships.
Which is historically accurate, to the best of my knowledge. They *did* run a bit too deep and the early magnetic pistols weren't worth much. My bad for not remembering my history.
